The Investigation Bureau on Thursday searched 23 TRA offices and summoned Huang, along with 18 other officials and businesspeople, for questioning.

A preliminary investigation suggests that Huang may have accepted more than NT$10 million (US$343,150) in bribes when he was overseeing the construction of the South Link Line, investigators said.

Huang, who graduated from the National Taiwan University’s Department of Civil Engineering in 1970, has been working at the railways agency since 1974.

Other TRA officials who were summoned for questioning included Chiang Teng-fan (江登凡), Hsu Sheng-tung (許勝通) and the former and current organizers of the South Link construction, Tseng Chien-kuo (曾建國) and Lai Yung-chien (賴永謙), the bureau said.

The owner and general manager of the contractor Chuan Sheng Construction Co — Lin Chun-sung (林春松) and You Yung-chin (游永欽) — were also summoned for questioning, the bureau added.

Huang is suspected of collaborating with Chuan Sheng, leaking crucial information to help the latter win the bid to rebuild a section of a bridge over the Taimali River (太麻里溪) which was destroyed by Typhoon Morakot in 2009.

The bureau said it had also discovered that after winning the bid, the company had outsourced the project to Hung Ta Construction Co and profited from the deal.

The bid that was involved in the alleged corruption charges totaled nearly NT$800 million, according to the bureau.

Another TRA deputy director-general, Chung Chao-hsiung (鍾朝雄), and six other officials were detained on Oct. 31.

Chung, who was in office for less than one month, was alleged to have close ties with contractors when he was serving as chief engineer at the TRA.

He was alleged to have, along with other officials, revealed the minimum price to contractors, provided them with altered construction plans, as well as increased the construction budget and delayed the start of the projects.

An initial investigation showed that officials were treated to weekly sexual favors costing about NT$3 million in total, which were shouldered by the contractor. Officials’ signatures for various visits were found in account books.

The Taichung District Court yesterday approved prosecutors’ requests of bail of NT$1 million for Huang and NT$100,000 each for Hsu and Lai. It also ruled that Tseng was to remain in detention and barred from having visitors. Lin and You were released on bail of NT$500,000 and NT$200,000 respectively.